180 EOYAL SOCIETY OF CANADA 



On the same date plate cultures were made in ash-maltose-agar 

 E102 and E82 from the agar in the flask and from the living roots^ 

 but these all remained negative after tAventy-four days. 



Flaslc TVII.— Was planted on December 12th, 1905, with one germ- 

 inating pea and one germinating vetch seed. The flask contained 250 

 grams of medium R83. The loss by evaporation during the 159 days 

 of growth was 22 grams, or .138 gram per day. 



Inoculation. — The flask was then inoculated with a pure culture 

 c£ Ps. radicicola obtained from a vetch nodule on July 6th, 1905, and 

 had been grown on medium E44 since July 12, 1905, a |)eriod of five 

 months. In twenty-four hours at room temperature there was good 

 growth of the organism on the agar and in the water of condensation. 



Growth. — Both plants grew well, the vetch more vigorously than 

 the pea.. On January 17th, 1906, there were six nodules on the vetch 

 and none on the pea. On March 23rd the largest nodule on the vetch 

 was 6 mm. long and clove-shaped. As the roots of both vetch and pea 

 penetrated the agar, the culture accompanied them and could be ob- 

 served as a cylinder of growth aroimd the roots. On May 10th the 

 final examination was made. The vetch was thrifty and green, with 

 two main stems, one 0.18 m. and the other 0.10 m. long, also other 

 branches, so that the total length of stem was about 0.5 m.' Photo- 

 graph 40, Flask No. 3, was taken February 10th, 1906, at which date 

 there were ten nodules on the vetch and none on the pea. 



From the medium Ps. radicicola was isolated in pure culture, sub- 

 culture and staining methods furnished proof of the identity. 



From the vetch three nodules were taken, the largest was 9 mm. 

 long, forking at a distance of 6 mm. from the proximal end into two 

 nearly equal branches, each about 2 mm. thick. The whole nodule 

 was deep green with chlorophyll except at the growing ends, which were 

 white. A section from the distal end showed a loose cortical layer 

 and a central mass of bacteroidal tissue, brownish in colour, and mainly 

 composed of bacteria. There were few simple rods, but many numerous 

 and beautifully branched and twice branched cells. Cultures obtained 

 from this nodule gave pure cultures of Ps. radicicola, confirmed by sub- 

 cultures and staining reactions (polar flagellum). Direct examination 

 of the other nodules and cultures therefrom gave identical results. Gen- 

 eral infection of the roots had also taken place, pure cultures of Ps. 

 radicicola were obtained from them. 



There were no nodules present on the pea. Four plates made from 

 the interior of the pea root were all negative. The following media,. 

 E82, E87 and E103 were used and plates kept fourteen days. 



